Clustered parachutes, which are not new in the art, offer several advantages over a single large parachute. One, clustered parachutes provide a shorter opening time and distance. Two, clustered parachutes are easier to fabricate and recover.
The major difficulty with clustered parachutes is that the parachutes in the cluster generally do not open simultaneously. A canopy (or some of the canopies) in a cluster will often inflate more rapidly than the other canopies in the cluster, thereby causing structural overloads on the early opening canopy (or canopies), and aerodynamic interference, which result in inflation difficulty in the late opening canopy (or canopies) and excessive filling times for the total cluster.
One method of preventing the above mentioned problems is to design a clustered parachute system wherein each individual parachute could withstand the entire opening force from the payload. Another method of preventing the above mentioned problems is to include additional or backup parachutes in the cluster to assure safe recovery of the payload. Both methods result in heavy, bulky, and expensive clustered parachute systems.
A better technique for avoiding structural overloads is to design clustered parachutes with canopies that will open, and inflate to the fully open position simultaneously. Even distribution of the opening force among all the parachutes in a cluster provides improved inflation stability and load control. This eliminates overloading and structural damage of the parachutes.
In view of the importance of uniform opening of clustered parachutes, others have developed means for controlling opening of canopies of clustered parachutes during descent.
Stencil teaches simultaneous opening of the canopies of clustered parachutes in U.S. Pat. No. 3,423,054. The Stencil apparatus includes a plurality of canopies which open when an explosive cartridge and its associated firing line-operated activator is activated. When the cartridges are ignited, the combustion gases drive pistons which accelerate projectiles radially outwardly. The accelerated projectiles are connected to the skirt portion of a canopy.
Pinnell teaches simultaneous opening of canopies of clustered parachutes in U.S. Pat. No. 4,780,970. The Pinnell apparatus includes a triangularly-shaped web, located centrally between the parachutes in the cluster, to provide control of the parachute skirts during deployment. Some of the parachute reefing rings of each parachute are held together by the web assembly to limit the opening of the parachute skirt. Pinnell teaches the use of several closed loop reefing lines disposed within a cutter.
Johnson teaches simultaneous opening of canopies of clustered parachutes in U.S. Pat. No. 4,752,050. The Johnson apparatus includes a single multi-line cutter connected to each parachute in a cluster by a separate short tether line. Johnson also teaches the use of several closed loop reefing lines that are threaded through the cutter.
While these earlier apparatus provide means for effecting the simultaneous opening of canopies in a clustered parachute system, the present invention provides an improved means which requires a minimal amount of added equipment, lacks the need for reefing line cutters, is substantially easier to pack than the prior apparatus, and, most importantly, yields reliable and substantially improved cluster opening.